The feet and the hands both include numerous bones and joints that cooperate together to define quintessential human movement. They are sophisticated, delicate and altogether elegant in function and design. Together the foot and ankle have over 25 bones and 33 joints along with more than 100 named muscles, tendons, and ligaments and a network of blood vessels, nerves, all residing beneath a relatively slim covering of soft tissue and skin. Structurally, the foot has three main anatomical regions: the forefoot, the midfoot, and the hindfoot. These parts work together with the ankle, to provide the body with support, balance, and mobility. A structural flaw or malfunction in any one part can result in the development of problems, which are manifested in other areas of the body. The hand forms a cognate to the foot with 27 bones within the hand and wrist. There are eight small bones within the wrist called the carpals, which join with the radius and the ulna to form the wrist joint. The carpals connect with the five metacarpals to form the palm of the hand, which terminate in the rays (i.e., the thumb and fingers) formed by the phalanges. The three phalanges in each finger are separated by two joints, called interphalangeal joints (IP joints). The one closest to the MCP joint (knuckle) is called the proximal IP joint (PIP joint). The joint near the end of the finger is called the distal IP joint (DIP joint). The thumb only has one IP joint between the two thumb phalanges. The IP joints of the digits also work like hinges when you bend and straighten your fingers and thumb.
Similarly, the forefoot includes the five toes (which are also known as the “phalanges”) and their connecting long bones (or “metatarsals”). Several small bones together comprise a phalanx or toe. Four of the five toes have three phalanx bones respectively connected by two joints. The big toe (or “hallux”) has two phalanx bones distal and proximal with a joint in between called the interphalangeal joint. The big toe articulates with the head of the first metatarsal at the first metatarsophalangeal joint (the “MTP” joint) and there are two tiny, round bones called sesamoids on the plantar side of the metatarsal head. The phalanges are connected to the metatarsals at the ball of the foot. The forefoot balances pressure on the ball of the foot and bears a substantial amount of the body weight.
The bones of the midfoot from medial to lateral are the 1st through 3rd cuneiform, the cuboid, and the crescent shaped navicular bone posterior to the cuneiforms, which also forms a joint with the talus that forms the basis for the ankle joint at the hinged intersection of the tibia, the fibula, and the foot. The five tarsal bones of the midfoot act together form a lateral arch and a longitudinal arch, which help to absorb shock. The plantar fascia (arch ligament) underlays the bones of the midfoot and along with muscles, forms a connection between the forefoot and the hindfoot. The toes and their associated midfoot bones form the first through fifth rays beginning with the great toe as the first ray. The bones which form the palmate portion of the hand are: the scaphoid, the lunate, the triquetrum, the pisiform, the trapezium, the trapezoid, the capitate, and the hamate, which act in concert to allow the opposition of the thumb with each of the fingers and to permit the uniquely human ability to manipulate objects.
The hindfoot is composed of three joints (subtalar, calcaneocuboid & talonavicular) and links the midfoot to the ankle. The heel bone (or “calcaneus”) projects posteriorly to the talus and forms a lever arm to activate the hinged action of the foot so as to allow propulsion of the entire body from this joint. The calcaneus is joined to the talus at the subtalar joint. The mid-foot is often the subject of trauma, such as results from falls, vehicle, crashes and dropped objects. These accidents often result in severe fractures and/or dislocations. In addition, there are several conditions which result from congenital deformation or which arise as a result of repeated use type injuries. Surgical intervention that includes surgical sectioning of bone or an “osteotomy” is often used to restructure the bones as a treatment for such conditions, for example, the bunionectomy. The present invention is likewise useful for conditions of the hand that result from prior trauma, surgical intervention or defects from birth or that develop with age (such as rheumatoid arthritis).
Examples of some of the other procedures with which the present invention could be used include hallus valgus and hallus rigidus corrections. Other applications which could use the present invention include first and fifth metatarsal chevrons, translational osteotomies, closing wedge osteotomies, pediatric femoral osteotomies, metacarpal and calcaneal rotational osteotomies, intrarticular osteotomies and hand and wrist realignment osteotomies. Specific surgical techniques are discussed for the use of an embodiment of the invention designed for use in bunionectomies.
Typical surgical treatment of the foot or hand re-establishes a normal anatomy while the fractured bones mend. In some cases, fusion of a joint may be necessary, for example, where arthritis arises in a patient due to use injuries, poor bone or prior unsuccessful surgeries. One current surgical treatment of these conditions requires that pins, wires and/or screws be inserted to stabilize the bones and joints and hold them in place until healing is complete. For example, a pin or screw may be introduced medially into the internal cuneiform and through the base of the second metatarsal bone. While the use of k-wires, pins, and screws may provide acceptable results for younger and more plastic patients, these methods of fixation are not always satisfactory.